There's no doubt that the biggest potential sufferers from a hard Brexit are the banks.
It's not just the import and export tariffs that would afflict every company that does business across the UK/EU border, but the very legality of their business itself -- if the banks lose their 'passporting' rights, they will simply lose the ability to provide a lot of their current EU-wide services.
And if that happens, profits will be hit hard.
It's no wonder that Lloyds Banking Group shares are down 24% since the eve of the referendum, to just 55p, nor that as Brexit has begun to look harder by the day they have given up even the modest recovery that took them back up a bit by early September.
Barclays has actually done better. After a big slump, its shares have regained most of their ground to 185p, possibly because Barclays has already slashed its dividends and investors are expecting the rest to follow -- but a passporting loss would surely give the shares another kicking.
Royal Bank of Scotland shares are down 24% since the big day too, to 188p, with the bank facing the prospect of another Scottish independence vote in addition to Brexit woes.
Not giving up
But the banks are not giving up their lucrative pan-European business without a fight.
According to the boss of the British Bankers' Association, Anthony Browne, writing in the Observer, the UK's big banks are already drawing up plans to move their headquarters out of the UK. And it could happen as early as next year -- waiting until there's a definite outcome from our Brexit negotiations could be way too late. Mr Browne added that "public and political debate at the moment is taking us in the wrong direction".
On the downside, that would lead to job losses in the UK -- and there would surely be a hit to the £65bn a year the sector contributes to the UK's tax coffers. But on the upside, other than a bit of turmoil that would have an effect on bottom-line profits during the transition, it would help secure the long-term profitability of the banks.
So what should investors do? We could sit tight and hope there's a quick move to an agreement on retaining passporting rights -- despite the apparent hardening of the mood in Europe. Or we could just be happy to accept the possibility of our banks deserting these shores if it's enough to keep our investment prospects looking healthy.
Alternatively, there's always HSBC Holdings, which conducts very little of its business in the region -- less than 5% of its 2015 profit came from the whole of Europe, with Asia accounting for around 85%. At 629p today, HSBC shares are up 38% since the EU referendum.
And then there's Virgin Money Holdings. Virgin Money, being a small retail bank in the UK aimed at British savers and British mortgage borrowers, shouldn't be too bothered about EU passporting rules -- its business is 100% within the UK.
The so-called challenger bank did see its shares crash after the vote, unfairly I'd say, and despite a strong recovery since then they're still down 9% at 333p -- so is that a buying opportunity? With strong earnings growth on the cards and the shares on forward P/E multiples of only around 10, I think so.
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Alan Oscroft owns shares of Lloyds Banking Group. The Motley Fool UK has recommended Barclays and HSBC Holdings. We Fools don't all hold the same opinions, but we all believe that considering a diverse range of insights makes us better investors.